Method for making wire drawing dies



Patented Mar. 25, 1941 PATENT OFFICE METHOD FOR MAKIIN SG WIRE DRAWING Edgar W. Engle, Grosse Pointc Park, and Hershel B. Duncan, Detroit, Mieli., assignors to Carboloy Company, Inc., Detroi New York t, Mich., a corporation of Application Api-:14, 1840, serial No. 327,816

4 Claims.

The present invention relates to amethod for making wire drawing dies and more particularly to a method for making Wire drawing dies in which the hole through the die nib is of very small diameter, for example of the order of about 0.015 inch or less. The prior Engle and Duncan patent application Serial No. 180,078, filed December 16, 1937, of which this application is a continuation in part, discloses and claiins a method for making wire drawing dies which method comprises the step of forcing a hard metal nib having a relatively low coeflicient of expansion into a softer steel casing slug having a relatively high coeflicient of expansion. In the prior process if a cored nib is forced into the steel casing slug the large diameter opening of the core is in contact with the plunger and the 'small diameter opening is in contact with the steel casing slug. As a result, when the nib is forced into the slug some of the steel from the slug is squirted into the small opening in the cored die. If the cored die has a relatively large opening therethrough the metal which has been forced into the opening shrinks and becomes loose during cooling and no difliculty is encountere'd in its removal. However, if -the die opening which is in contact with the steel casing slug is small, for example of uthe order of about 0.015 inch or less, the shrinkage of the casing metal forcedinto 'this opening isnot suflicient to permit its readyremoval upon cooling and its elimination is expensive and time consuming. z

It is one of the objects of the present invention to provide an improved method for forming small hole wire drawing dies. A further object of the invention is to provide in such a method means for preventing metal from the casing slug entering the small opening in the cored die nib.`

The novel features which are characteristic of our invention are set forth with particularity in the appended claims. The invention, however,

-will best be understood from reference to the following specification when considered in connection with the acoompanying drawing in which Flg. 1 is a Vertical sectional view of a forging die holder, associated structure and a blank or slug of casing material showing a cored nib and plunger in` position prior to forcing the nib into vthe slug; Fig. 2 is a Vertical cross sectional view of the slug and nib after the nib has been forced into the slug; Fig. 3 is a Vertical cross sectionalL view of the slug and nib after the upper portion of the casing slug has been forged over the cored nib while Fig. 4 is a Vertical cross sectional view 65 of the finished nib and casing therefor.

Referring more particularly to the drawing, we have indicated at |0 a steel forging die having a central opening I l therethrough W'hich opening is positioned in alignment with a hole |2 which" extendsthrough a support |3. The opening ll is tapered slightly with the larger diameter at the top of the die. The taper is in general of the order of .020 inch per inch. A steel bottom plate M placed in the opening H rests on the support |3. The plate ['4 has a substantially conical depression I 5 in its upper surface.

In operation, a steel casing slug I 8 is heated 'to a suitable forgingtemperature, for example about 1850 to 2000 F. to make it plastic and then placed in the opening of the forgingvdie and on top of the bottom plate |4. The slug |6 when heated at this temperature fits closely within the opening ll which limits lateral expansion of the slug. A centering plate |1 having a central opening |8 therethrough is positioned on -the upper end of -the forging die |0. The opening |8 in plate l'l is coaxial with the opening ll. I A cemented carbide cored nib IS having a substantially conical or bell-shaped'opening therein is positioned in the opening |8 of plate l'l and on 25 top of the heated slug IS so that the largest diameter of the die opening is in contact with the heated slug. Pressure is applied to the nib |'9 by a plunger 20 to thereby sink the nib below the top surface of the slug IS. The excess metal in the slug flows into the conical opening IS in the base plate forming a conical portion 2| on the casing IG. As a result of the ilow of metal into the depression |5 only a very small quantity of metal enters the opening in the die nib. The 35 upper end-of the casing IB may be forged over the upper end of the die nib in the manner dis- `closed in the prior Engle and Duncan patent application Serial No. 180,078.

After the casing IB has been forged over the 40 end of the nib |9, the casing IG and enclosed nib are ejected from the forging die by lthe application of pressure to` the base plate H through the opening |2 in the support |3. The encased nib may be'tempered at about 900 F. to l250 F. to develop desired properties in the casing steel. The conical metal portion 2| of the casing IB is now removed, and the desired final form of central opening completed in the die nib and casing IG. A small quantity of metal may enter the lower or large opening in the cored nib when the nib is forced into the slug IG. However, such metal is only loosely held in the opening. and drops out when the desired opening is made through the -nib and casing. No metal enters the small opening in the cored nib' during the process of" forming the die.

The hard metal nib IS preferably is a cemented carbide material. Such carbides have a very low coeflicient of expansion. These carbides also are well known and are formed by pressing and sintering the mixed ingredients. They generally consist of one or more hard carbides bonded or cemented .together Aby lower melting point inetal. In general, we prefer to employ a cemented ear- 'bide nib consisting substantially of tungsten carbide and cobalt, the eobalt content of the cemented carbide generally being less than 20%\. The casing slug material employed preferably is a steel having a relatively high coeflicient of, expansion. A steel suitable. for such use is disclosed, in our prior application Serial No. 180,078 and may contain about 0.80% to/1.05% carbon, about 0.20% to 0.45% vanadium and if desired up to about 0.5% chromium. w

What we claim as new and desire to secure by Letters Patent of the United States is:

l. The method of making a wire drawing die which comprises heating a steel casing slug to a forging temperature, placing said slug in a forging die and on top of a base plate having a depression therein, positioning a cored nib on saidl slug and in allgnment with said depression and applying pressure to said nib to force the nib completely into the heated slug and the excess metal in said slug into said depression to thereby limit the fiow of metal into the opening in the nib.

2. The method of making a wire drawing die which comprises heating a steel caslng slug to a forging temperature, placing said slug in a forging die and on top of a base plate having a depression therein, positioning a cored nib on said slug, said cored nib having a substantially conicalopening therein the widest portion of said opening being in contact with the heated slug, and applying pressure to the cored nib to force the nib l'completely into said heated slug and the excess metal insaid slug into said depression to 5 thereby limit the flow of metal into the opening in the nib.

3. The method of making a wire drawing die which comprises heating a steel casing slug having a relatively high coemcient of expansion to a forging temperature, placing said slug in a forging die and on top of a base plate having a central depression in the upper surface thereof, positioning a cored cemented carbide nib having a relatively low coefllcient of expansion on said 15 slug and in alignment with said depression. and applying pressure to the cored nib to force the nib completely into the heated slug and the excess metal in said slug into said central depression to thereby limit the flow of metal into the 20 opening in the nib.

4.' The method of making a wire drawing die which comprises placing in a forging die a base plate having a substantially conical depression in the upper end thereof, placing a steel casing slug 25 heated'to a forging temperature in said die and on top of said base plate, positioning a cored die nib on said heated slug, said nib having a substantially a conical. opening extending therethrough, the widest, portion of said opening being 30 in` contact with said slug and in alignment with said conical depression and applying pressure to said cored nib to force the nib completely into said heated slug and the excess metal in said slug into said oonical depression to thereby limit the flow of metal into the opening in the nib.

EDGAR W. ENGLE. HERSHEL B. DUNCAN. 

